I very much like early exits ( return, next,last ) when they avoid getting deep into stuff, especially dealing with exceptions, errors, irregularities. This example allows empty lines and comments in a data file.

open my $datafile ... 
LINE:
while ( my $line = <$file> ) {
    next LINE unless length $line;
    next LINE if ( $line =~ m{\A \s* #}xms;
    process $line;
}
[download]

If you're selecting one of several possible return values, I think it better to determine the value and return it in a single place. Otherwise you have a situation where a return value of XYZ may have arisen from this return statement or from that return statement. If the blocks are more than a few lines long, it may be worth encapsulating it into a named subroutine. That way the main block is short and easy to read:

if ( option_A( $line ) ) {
   $retval = do_this_complicated_thing( $line );
}
elsif ( option_B( $line ) {
   retval = 'alphagetti';
   retval .= ' and maple syrup' 
      if $option_C( $line );
}
else {
    $retval = 42;
}
return $retval;
[download]